1. Field of the Invention
The present invention relates to inspecting the integrity of fasteners, and, more particularly, the present invention relates to a device fir and method of inspecting fasteners in their environment of use.
2. Description of the Related Art
A typical requirement for industrial facilities, regardless of the type of industry, is that the equipment must be inspected on a routine basis to ensure that the structural integrity of the equipment is within acceptable guidelines. While the frequency of such inspections may vary, the need to prevent failure or break-down of the equipment is a common requirement across industry. For exemplary purposes, the environment of a nuclear utility will be discussed herein.
Nuclear utilities have a need to verify the integrity of their aging components within nuclear reactors and other plant systems. In Pressurized Water Reactors (PWRs), one exemplary set of components required to be inspected for plant life extension and compliance with regulatory requirements are the baffle bolts that are part of the reactor internal assembly. Due to the bolt pre-loads, age, and radiation fluence through the bolts, these fasteners are susceptible to loosening and cracking. Moreover, due to radiation embrittlement of the bolt materials (irradiation-assisted stress corrosion cracking, or IASCC), once a crack begins, it can grow quickly due to the reduced toughness of the embrittled material. Other influences may subject equipment in other types of facilities to similar degradation.
Industrial facilities typically have reduced access to fasteners once the equipment and related components are placed in service. In the environment of a nuclear power plant, retaining bars and/or washers are welded to the top of fasteners to prevent them from falling out if they become loose or if the head portion becomes detached from the shaft. These safety precautions make fastener inspection much more difficult and complex. Without a qualified and reliable inspection of the fasteners in their use configuration, the safety components must be removed to physically access the fastener. Thus, the facility operators will replace these fasteners regardless of whether they actually need to be replaced. Replacement, of course, is a much more costly and time consuming undertaking.
Thus, there is a need for a reliable and capable inspection system and method for fasteners with limited access.